title: Foveal anatomic associations with the secondary peak and the slope of the macular pigment spatial profile.
abstract: OBJECTIVE
  To investigate the reproducibility of the macular pigment (MP) spatial profile by using heterochromatic flicker photometry (HFP) and to relate the MP spatial profile to foveal architecture.
  
  
  METHODS
  Sixteen healthy subjects (nine had the typical exponential MP spatial profile [group 1]; seven had a secondary peak MP spatial profile [group 2]) were recruited. The MP spatial profile was measured on three separate occasions. Six radiance measurements were obtained at each locus (0.25 degrees , 0.5 degrees , 1 degrees , and 1.75 degrees eccentricity; reference point, 7 degrees ). Foveal architecture was assessed by optical coherence tomography (OCT).
  
  
  RESULTS
  Subjects who had the typical decline profile, had this profile after averaging repeated measures (group 1). Subjects who had a secondary peak, displayed the secondary peak after repeated measures were averaged (group 2). Mean SD foveal width in group 1 was significantly narrower than mean SD foveal width in group 2 (1306 +/- 240 microm and 1915 +/- 161 microm, respectively; P < 0.01). This difference remained after adjustment for sex (P < 0.001). Foveal width was significantly related to mean foveal MP, with adjustment for sex (r = 0.588, P = 0.021). Foveal profile slope was significantly related to MP spatial profile slope, after removal of an outlier (r = 0.591, P = 0.020).
  
  
  CONCLUSIONS
  HFP reproducibly measures MP spatial profile. Secondary peaks seen in the MP spatial profile cannot be attributed to measurement error and are associated with wider foveas. The slope of an individual's MP spatial profile is related to foveal slope, with a steeper MP distribution associated with a steeper foveal depression.
authors.affiliation: Department of Chemical and Life Sciences, Waterford Institute of Technology, Waterford, Ireland. mlkirby@wit.ie
authors.forename: Mark L
authors.initials: ML
authors.lastname: Kirby
authors.forename: Martin
authors.initials: M
authors.lastname: Galea
authors.forename: Edward
authors.initials: E
authors.lastname: Loane
authors.forename: Jim
authors.initials: J
authors.lastname: Stack
authors.forename: Stephen
authors.initials: S
authors.lastname: Beatty
authors.forename: John M
authors.initials: JM
authors.lastname: Nolan
mesh_terms: D005260:Female; D005584:Fovea Centralis / Q000033:anatomy & histology* / Q000737:chemistry*; D006801:Humans; D014975:Lutein / Q000032:analysis*; D008297:Male; D010783:Photometry / Q000379:methods; D015203:Reproducibility of Results; D012168:Retinal Pigments / Q000032:analysis*; D041623:Tomography, Optical Coherence; D024341:Xanthophylls / Q000032:analysis*; D065146:Zeaxanthins
chemical_list: D012168:Retinal Pigments; D024341:Xanthophylls; D065146:Zeaxanthins; D014975:Lutein